Hello,
For skills I would consider:
1) Once a week take an few hours and mentally complete the process of planning, preparing, diving, and post dive efforts for a deep technical dive with deco. Add an overhead environment if you normally dive them. Run through a number of different emergencies. Make this as detailed as possible in your mind -- mentally complete each step and movement Even better, close your eyes and mime the movements as you do each part of the dive. One of my rebreather instructors said that, as far as proficiency and skills are concerned, studies show this is almost as good as actually doing it.
2) Read at least one book a month on the details, physics, methods, etc of technical and rebreather diving. Read books with detail and information you think you know and challenge yourself to find something you forgot or remembered incorrectly.
3) Once a month run through all the paperwork, formulas, charts, software, etc used to properly plan a complicated dive. Do it all by the book even if you don't normally do it for your dives.
4) Once a week read and consider all the details of at least one dive accident or incident for which substantial details have been reported. Consider the accident chain and how you might change your diving to prevent a similar event in your diving.
5) If your computer and/or controllers lets you, put them in simulation mode and run a dive on the couch once a month. Run through all the menus and enter and select different gas profiles.
6) If you're qualified and able, teach a quarterly class on some dive subject. Nothing teaches someone more about a subject than teaching.
7) Take an advanced first aid class or refresher.
8) Write an article or two about diving for rebreather world. Either technical or a story about a close call or learning experience you had while diving.
9) Mentor someone new to rebreathers. Help them select equipment.
10) Take one of your past instructors to dinner and drinks and thank them for helping keep you alive. Preferably take the one that never stops telling stories. Try to learn two critical safety-related lesson from each of the stories they tell. I can recommend a few story tellers if you'd like.
Have fun doing this stuff.
Sincerely,
Paul